Radio frequency (RF) and microwave systems often employ frequency conversion configured to track an input RF signal over a range of frequencies. For example, in a network analyzer, a local oscillator (LO) signal is often configured to track a frequency of an RF test signal to facilitate s-parameter measurements. In particular, by frequency tracking, the LO signal can be used to convert (e.g., downconvert) one or both the RF test signal and a response signal of a device under test (DUT) to a fixed intermediate frequency (IF). The fixed IF may simplify an implementation of a measurement portion or ‘test set’ of the network analyzer, for example, as well as support high performance characteristics of the network analyzer measurement portion.
Unfortunately, as DUT bandwidth and concomitant frequency range requirements of modern RF/microwave systems increase, a tuning range of the RF test signal and tracking LO signal must be similarly increased. However, with conventional frequency-tracking signal synthesis and the signal sources that use such synthesis (e.g., phase-locked loop RF sources) it can be difficult to achieve frequency tuning ranges sufficient to meet the needs many modern RF/microware systems.